The invention relates to a method of operating a hybrid drive train of a motor vehicle having an internal combustion engine connectable, via a first clutch, to a transmission and an electric machine which can be connected to the internal combustion engine via a second clutch and, via a third clutch, to the transmission without interposition of the first clutch.
DE 103 19 880 A1 describes a hybrid drive train of a motor vehicle in which a first clutch in the form of a wet starting clutch is arranged between an internal combustion engine and a transmission in the form of an automatic transmission. The drive train has a first electric machine which is directly connected for rotation with an output shaft of the internal combustion engine. The drive train also has a second electric machine. The second electric machine can be connected by means of a clutch to a ring gear of an input planetary gear set of the automatic transmission, to which the internal combustion engine can also be connected by means of the starting clutch. In addition, the second electric machine can be connected by means of a further clutch to a sun gear of the input planetary gear set. The first electric machine is thereby fixedly connected to the internal combustion engine, and the second electric machine can be connected to the transmission without the interposition of the starting clutch. A plurality of different operating modes can be implemented using said drive train.
It is the object of the present invention to provide a method of operating a hybrid drive train of a motor vehicle in a cost-effective and reliable manner selectively by the internal combustion engine or an electric machine or both, or driving the electric machine selectively by the engine or the vehicle depending on different operating modes.